Effect of Gamma and Alpha Irradiation on the Corrosion of the French Borosilicate Glass SON 68
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Abdesselam Abdelouas1, Karine Ferrand1, Bernd Grambow1, Thierry Mennecart1, Massoud Fattahi1, Gilbert Blondiaux2 and Chantal Houée-Lévin3 1 SUBATECH (UMR 6457), Ecole des Mines de Nantes, 4, rue Alfred Kastler, B.P. 20722 44307 Nantes cedex 3, France. 2 Centre d'Etude et de Recherche par Irradiation / 3A, rue de la Férollerie, 45071 Orléans cedex 2, France. 3 Université Paris Sud, Laboratoire de Chimie Physique, Bat.350, 91405 Orsay, France. $%675$&7 Corrosion experiments with the French borosilicate glass SON 68 were conducted under gamma (60Co source) and alpha (cyclotron) irradiation conditions. Static tests with glass powder were conducted at 90°C under saturation conditions with synthetic solutions rich in Si, B and Na. The initial pH was 9.8 and the SA/V was 3970 m-1. For gamma irradiation tests with the highest dose (∼ 58000 Gy) the pH decreased by almost a unit, which lasted for two weeks. The ionexchange between glass and solution was enhanced as evidenced by the increase of the Linormalized mass loss within 93 days. The measured H2O2 concentration in the experiment with the glass was as high as 1.51 10-5 M. The alpha irradiation tests with a total dose of 1800 Gy did not affect the solution pH and therefore the leaching rate of the glass remained similar to that in the blank experiment after 59 days. However, the measured H2O2 concentration was as high as 2.32 10-5 M. This work indicates that high irradiation doses may enhance the ion-exchange process due to the pH decrease.
,1752'8&7,21 The effect of radiation on waste form stability is a critical concern for disposal safety [1]. Radiation effects in a solid phase include formation of point defects, radiation enhanced diffusion, change in mechanical properties, volume changes, phase transformations, phase separation, microfracturing and formation of gas bubbles. In addition, in the presence of water, radiolysis can produce molecular and radical water decomposition products that may affect the corrosion rate of the waste form. The impact of gamma- and alpha-irradiation on nuclear waste glass corrosion has been investigated by several authors [2-4]. Some of the experiments were conducted under static conditions and using either actinides-doped glasses, heavy ionsimplantation or external gamma sources. Doping glasses may affect the chemistry of the glass/solution system and thus the resulting chemical effect may interfere with the direct effect of the radiation. Some work concluded that no significant effect was observed [5] while others showed that irradiation enhanced the ion-exchange because of H3O+ and/or bubbles production [4,6-7]. We investigated the effect of α- and γ-irradiation on the corrosion of the French simulated nuclear waste glass SON68 under saturation conditions, where the glass matrix corrosion is very slow and leaching is controlled by water diffusion and ion-exchange. In addition, within the
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duration of our experiments, satu
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